Posttranslational Modifications of NPR1: A Single Protein Playing Multiple Roles in Plant Immunity and Physiology

What makes a protein a good immune regulator? We can make some intuitive guesses based on the characteristics of an immune response. Because immunity is not only dangerous to the pathogen but also potentially harmful to self, its regulators should only be active when the threat of infection is imminent, and their activities should be spatially and temporally appropriate to the infection pressure. In-depth studies of the plant immune regulator non-expressor of pathogenesis-related (PR) genes 1 (NPR1) have revealed the molecular mechanisms contributing to these characteristics and also discovered some surprising connections that the immune system has to normal plant physiological processes to minimize the fitness costs. Because NPR1 transcription is not dramatically affected by pathogen challenge [1], studies of NPR1 have been focused on posttranslational modifications (PTMs). By analogy, NPR1 is like an actor who plays many roles by wearing different costumes.